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The x86 Shadow stack feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. One of these unusual properties is that shadow stack memory is writable, but only in limited ways. These limits are applied via a specific PTE bit combination. Nevertheless, the memory is writable, and core mm code will need to apply the writable permissions in the typical paths that call pte_mkwrite(). The goal is to make pte_mkwrite() take a VMA, so that the x86 implementation of it can know whether to create regular writable or shadow stack mappings. But there are a couple of challenges to this. Modifying the signatures of each arch pte_mkwrite() implementation would be error prone because some are generated with macros and would need to be re-implemented. Also, some pte_mkwrite() callers operate on kernel memory without a VMA. So this can be done in a three step process. First pte_mkwrite() can be renamed to pte_mkwrite_novma() in each arch, with a generic pte_mkwrite() added that just calls pte_mkwrite_novma(). Next callers without a VMA can be moved to pte_mkwrite_novma(). And lastly, pte_mkwrite() and all callers can be changed to take/pass a VMA. Start the process by renaming pte_mkwrite() to pte_mkwrite_novma() and adding the pte_mkwrite() wrapper in linux/pgtable.h. Apply the same pattern for pmd_mkwrite(). Since not all archs have a pmd_mkwrite_novma(), create a new arch config HAS_HUGE_PAGE that can be used to tell if pmd_mkwrite() should be defined. Otherwise in the !HAS_HUGE_PAGE cases the compiler would not be able to find pmd_mkwrite_novma(). No functional change. Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/lkml/CAHk-=wiZjSu7c9sFYZb3q04108stgHff2wfbokGCCgW7riz+8Q@mail.gmail.com/ Link: https://lore.kernel.org/all/20230613001108.3040476-2-rick.p.edgecombe%40intel.com
145 lines
3.2 KiB
C
145 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* IBM System z Huge TLB Page Support for Kernel.
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*
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* Copyright IBM Corp. 2008
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* Author(s): Gerald Schaefer <gerald.schaefer@de.ibm.com>
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*/
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#ifndef _ASM_S390_HUGETLB_H
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#define _ASM_S390_HUGETLB_H
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#include <linux/pgtable.h>
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#include <asm/page.h>
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#define hugetlb_free_pgd_range free_pgd_range
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#define hugepages_supported() (MACHINE_HAS_EDAT1)
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void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep, pte_t pte);
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pte_t huge_ptep_get(pte_t *ptep);
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pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
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unsigned long addr, pte_t *ptep);
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/*
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* If the arch doesn't supply something else, assume that hugepage
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* size aligned regions are ok without further preparation.
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*/
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static inline int prepare_hugepage_range(struct file *file,
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unsigned long addr, unsigned long len)
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{
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struct hstate *h = hstate_file(file);
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if (len & ~huge_page_mask(h))
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return -EINVAL;
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if (addr & ~huge_page_mask(h))
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return -EINVAL;
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return 0;
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}
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static inline void arch_clear_hugepage_flags(struct page *page)
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{
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clear_bit(PG_arch_1, &page->flags);
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}
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#define arch_clear_hugepage_flags arch_clear_hugepage_flags
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static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep, unsigned long sz)
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{
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if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
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set_pte(ptep, __pte(_REGION3_ENTRY_EMPTY));
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else
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set_pte(ptep, __pte(_SEGMENT_ENTRY_EMPTY));
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}
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static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
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unsigned long address, pte_t *ptep)
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{
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return huge_ptep_get_and_clear(vma->vm_mm, address, ptep);
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}
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static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
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unsigned long addr, pte_t *ptep,
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pte_t pte, int dirty)
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{
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int changed = !pte_same(huge_ptep_get(ptep), pte);
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if (changed) {
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huge_ptep_get_and_clear(vma->vm_mm, addr, ptep);
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set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
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}
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return changed;
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}
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static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
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unsigned long addr, pte_t *ptep)
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{
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pte_t pte = huge_ptep_get_and_clear(mm, addr, ptep);
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set_huge_pte_at(mm, addr, ptep, pte_wrprotect(pte));
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}
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static inline pte_t mk_huge_pte(struct page *page, pgprot_t pgprot)
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{
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return mk_pte(page, pgprot);
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}
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static inline int huge_pte_none(pte_t pte)
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{
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return pte_none(pte);
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}
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static inline int huge_pte_none_mostly(pte_t pte)
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{
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return huge_pte_none(pte);
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}
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static inline int huge_pte_write(pte_t pte)
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{
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return pte_write(pte);
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}
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static inline int huge_pte_dirty(pte_t pte)
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{
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return pte_dirty(pte);
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}
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static inline pte_t huge_pte_mkwrite(pte_t pte)
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{
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return pte_mkwrite_novma(pte);
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}
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static inline pte_t huge_pte_mkdirty(pte_t pte)
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{
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return pte_mkdirty(pte);
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}
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static inline pte_t huge_pte_wrprotect(pte_t pte)
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{
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return pte_wrprotect(pte);
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}
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static inline pte_t huge_pte_modify(pte_t pte, pgprot_t newprot)
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{
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return pte_modify(pte, newprot);
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}
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static inline pte_t huge_pte_mkuffd_wp(pte_t pte)
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{
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return pte;
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}
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static inline pte_t huge_pte_clear_uffd_wp(pte_t pte)
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{
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return pte;
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}
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static inline int huge_pte_uffd_wp(pte_t pte)
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{
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return 0;
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}
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static inline bool gigantic_page_runtime_supported(void)
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{
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return true;
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}
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#endif /* _ASM_S390_HUGETLB_H */
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